PINGing an embedded system - PPP

This is a discussion on PINGing an embedded system - PPP ; I'm PINGing an embedded system from XP over a SLIP encoded serial link. Below are example outward and inbound packets that have been sent to and received from my embedded system. As far as I can make out the response ...

+ Reply to Thread
Results 1 to 6 of 6

Thread: PINGing an embedded system

  1. PINGing an embedded system

    I'm PINGing an embedded system from XP over a SLIP encoded serial link.
    Below are example outward and inbound packets that have been sent to and
    received from my embedded system. As far as I can make out the response is
    good but the PING always tells me it's timed out. I'm probably missing
    something obvious here. If anyone who knows about IP can tell me what the
    problem is I'd be grateful.

    Thanks.

    Rog.

    Request IP/ICMP packet:

    C0
    45 00 00 3C
    C4 8C 00 00
    80 01 60 30
    0A 01 01 01
    0A 01 01 02
    08 00 49 5C
    03 00 01 00
    61 62 63 64
    65 66 67 68
    69 6A 6B 6C
    6D 6E 6F 70
    71 72 73 74
    75 76 77 61
    62 63 64 65
    66 67 68 69
    C0

    Reply IP/ICMP packet:

    C0
    45 00 00 3C
    C4 8C 00 00
    80 01 60 30
    0A 01 01 02
    0A 01 01 01
    00 00 FB FF
    03 00 01 00
    61 62 63 64
    65 66 67 68
    69 6A 6B 6C
    6D 6E 6F 70
    71 72 73 74
    75 76 77 61
    62 63 64 65
    66 67 68 69
    C0



  2. Re: PINGing an embedded system

    In article ,
    Roger wrote:
    >I'm PINGing an embedded system from XP over a SLIP encoded serial link.
    >Below are example outward and inbound packets that have been sent to and
    >received from my embedded system. As far as I can make out the response is
    >good but the PING always tells me it's timed out. I'm probably missing
    >something obvious here. If anyone who knows about IP can tell me what the
    >problem is I'd be grateful.
    >
    >Thanks.
    >
    >Rog.
    >
    >Request IP/ICMP packet:
    >
    >C0
    >45 00 00 3C >C4 8C 00 00 >80 01 60 30 >0A 01 01 01 >0A 01 01 02
    >08 00 49 5C >03 00 01 00
    >61 62 63 64 >65 66 67 68 >69 6A 6B 6C >6D 6E 6F 70 >71 72 73 74
    >75 76 77 61 >62 63 64 65 >66 67 68 69
    >C0
    >
    >Reply IP/ICMP packet:
    >
    >C0
    >45 00 00 3C >C4 8C 00 00 >80 01 60 30 >0A 01 01 02 >0A 01 01 01
    >00 00 FB FF >03 00 01 00

    ^^^^^
    ICMP checksum
    >61 62 63 64 >65 66 67 68 >69 6A 6B 6C >6D 6E 6F 70 >71 72 73 74
    >75 76 77 61 >62 63 64 65 >66 67 68 69
    >C0


    You seem to have computed the ICMP checksum as 0xfbff. I'm pretty sure the
    ICMP checksum should be 0x515c.

    ========= For LAN/WAN Protocol Analysis, check out PacketView Pro! =========
    Patrick Klos Email: patrick@klos.com
    Klos Technologies, Inc. Web: http://www.klos.com/
    ==== Read up on Usenet etiquette: http://www.faqs.org/usenet/index.html ====

  3. Re: PINGing an embedded system


    "Roger" wrote in message
    news:dVwOd.669$%r5.290@newsfe1-win.ntli.net...
    > I'm PINGing an embedded system from XP over a SLIP encoded serial link.
    > Below are example outward and inbound packets that have been sent to and
    > received from my embedded system. As far as I can make out the response is
    > good but the PING always tells me it's timed out. I'm probably missing
    > something obvious here. If anyone who knows about IP can tell me what the
    > problem is I'd be grateful.
    >
    > Thanks.
    >
    > Rog.
    >
    >

    Grab a copy of ethereal network analyser (it's free), will show you all the
    components of request and response including checksums and whether or not
    they're correct. See www.ethereal.com.

    Cheers,
    Alf



  4. Re: PINGing an embedded system

    pklos@osmium.mv.net (Patrick Klos) wrote in
    news:cueajn$g90$1@pyrite.mv.net:

    Roger,
    You might want to take a look at RFC 1701, "Computing the Internet
    Checksum" - it talks about computing the checksum for IP, ICMP, IGMP,
    UDP, and TCP. I had a checksum bug once in an implementation of IGMP,
    so it does happen.


    > In article ,
    > Roger wrote:
    >>I'm PINGing an embedded system from XP over a SLIP encoded serial
    >>link. Below are example outward and inbound packets that have been
    >>sent to and received from my embedded system. As far as I can make out
    >>the response is good but the PING always tells me it's timed out. I'm
    >>probably missing something obvious here. If anyone who knows about IP
    >>can tell me what the problem is I'd be grateful.
    >>
    >>Thanks.
    >>
    >>Rog.
    >>

    .....

    >>Reply IP/ICMP packet:
    >>
    >>C0
    >>45 00 00 3C >C4 8C 00 00 >80 01 60 30 >0A 01 01 02 >0A 01 01 01
    >>00 00 FB FF >03 00 01 00

    > ^^^^^
    > ICMP checksum
    >>61 62 63 64 >65 66 67 68 >69 6A 6B 6C >6D 6E 6F 70 >71 72 73 74
    >>75 76 77 61 >62 63 64 65 >66 67 68 69
    >>C0

    >
    > You seem to have computed the ICMP checksum as 0xfbff. I'm pretty
    > sure the ICMP checksum should be 0x515c.
    >
    > ========= For LAN/WAN Protocol Analysis, check out PacketView Pro!
    > =========
    > Patrick Klos Email: patrick@klos.com
    > Klos Technologies, Inc. Web: http://www.klos.com/
    > ==== Read up on Usenet etiquette:
    > http://www.faqs.org/usenet/index.html ====



  5. Re: PINGing an embedded system


    "Unbeliever" wrote in message
    news:420b4d78$0$5725$afc38c87@news.optusnet.com.au ...
    >
    > "Roger" wrote in message
    > news:dVwOd.669$%r5.290@newsfe1-win.ntli.net...
    >> I'm PINGing an embedded system from XP over a SLIP encoded serial link.
    >> Below are example outward and inbound packets that have been sent to and
    >> received from my embedded system. As far as I can make out the response
    >> is
    >> good but the PING always tells me it's timed out. I'm probably missing
    >> something obvious here. If anyone who knows about IP can tell me what the
    >> problem is I'd be grateful.
    >>
    >> Thanks.
    >>
    >> Rog.
    >>
    >>

    > Grab a copy of ethereal network analyser (it's free), will show you all
    > the
    > components of request and response including checksums and whether or not
    > they're correct. See www.ethereal.com.
    >
    > Cheers,
    > Alf
    >
    >


    Thanks for your comments. I'll sort out the CS problem. It's typical that
    I've been looking at this for ages but miss the obvious problem!

    Ethereal is a good idea but unfortunately it doesn't capture data from SLIP
    serial links.

    Rog.



  6. Re: PINGing an embedded system

    Roger wrote:
    >
    > Ethereal is a good idea but unfortunately it doesn't capture data from SLIP
    > serial links.


    I have found that using tcpdump on a Linux box is invaluable in
    troubleshooting such connections. Don't let the name fool you -- it's
    particularly good with low level stuff like PPP negotiations. You might
    find it worthwhile to keep a Knoppix CD around (bootable Linux) just for
    that purpose if it doesn't suit you to actually install the OS on one of
    your computers.

    Ed


+ Reply to Thread